Added shadow database url to prisma

[michaelsieminski]

Summary

In some databases such as https://neon.tech its required to add a Shadow Database URL in Prisma for the migration to work.

This PR adds a DATABASE_SHADOW_URL to the .env.example file and uses it in the prisma schema file

• My code follows the code style of this project and passes {style_guide_run_command}.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change has adequate Unit Test coverage.

[homanp]

Thanks @1CAMOU 💯